1. Field of the Invention
This invention relates generally to a component mounting bracket and, more specifically, to an overhanging component positioner for precisely positioning a first component, such as a sensing device, over another component, where the first component can be temporarily pivoted out of the way of access to the second component and then easily and precisely repositioned back over the first component.
2. Background of the Invention
Automated manufacturing and packaging techniques often require the tracking of articles of manufacture as they progress through the manufacturing and packaging processes. This can be accomplished using optical transducers such as a photodiode emitter and receiver pair using the articles of manufacture as a reflector or diffuser to make or break the optical circuit. The range of these optics can be extended using fiber optic waveguides to position the sensing point at remote locations and in crowded environments. Lenses are also employed to focus and/or collimate the light for more accurate detection. One of the most difficult problems one faces when employing these kinds of position sensors is the accurate positioning and calibration of the sensors. Retooling and maintenance of the manufacturing line has meant that the sensors had to be removed to allow access to the underlying tooling and then repositioned and calibrated, if necessary, once the changes or maintenance was completed. Additionally, retooling to accommodate different package sizes has traditionally meant moving a substantial portion of each sensor from one location to another.
A particularly acute example of this problem occurs in an automated semiconductor chip marking device. One of the most effective chip marking devices uses a laser beam to mark the surface of the chip package. Unlike ink stamping, laser marking is fast, requires no curing time, and produces a consistently high-quality mark with minimal set-up time. In these devices, the laser beam burns a mark into the surface of the article of manufacture to produce a permanent mark, in contrast to inked marks, which may smear, degrade, fade or wear off. In the case of a packaged chip, the laser marking creates a different reflectivity from the rest of the package surface. Thus, by holding the chip at an angle to a light source, the information inscribed on the chip by the laser can easily be read.
Various machines and methods have been developed for marking a chip or other article of manufacture with a laser. As illustrated in U.S. Pat. No. 5,357,077 to Tsuruta, a plurality of semiconductor devices are placed in a tubular holder and transported by a coextensive group of conveyor belts to a laser for marking. Similarly, in U.S. Pat. No. 4,638,144 to Latta, Jr., electronic parts in the form of strips of lead frame supported components are conveyed to a laser marking station in magazines, unloaded, laser marked, and then reloaded into magazines. Likewise in U.S. Pat. No. 4,375,025 to Carlson, a strip of electronic components is conveyed by drive wheels to and from a position where a laser beam inscribes various characters or other information on the component surfaces. U.S. Pat. No. 4,370,542 to Mills et al. discloses a laser marking apparatus for marking a cable. The apparatus sequentially moves laterally adjacent cables along a marking platen and selectively positions and operates a laterally translatable laser to mark a stationary cable portion while another cable portion is being moved.
These devices require accurate indexing and positioning of the individual manufactured parts and the laser itself. The laser marking apparatus described and shown in the "Detailed Description of the Invention" section which follows, is capable of marking two separate rows of several individual parts at a time. Accordingly, the marking apparatus must count, position and track many parts. Additionally, the marking device uses gravity channels or tracks to guide the chips into position for marking and reloading into the chip carrying tubes. These tracks must be changed out for different sized chip packages which means that any other components which obstruct the removal and replacement of the tracks, such as the optical sensors, must be removed and reinstalled, often in a different location to accommodate the different package size, each time a different sized package is processed. The sensors often obstruct the removal and replacement of the tracks because it is desirable to position sensors, especially optical sensors, as close to the objects to be sensed as possible. Also, because the sensors must rely on a nearly perpendicular reflective surface, they are usually installed directly above the path in which the packages flow since mounting the sensors in the tracks is impractical and interferes with track integrity. Unfortunately, this often results in the sensors interfering with other subsystems such as machine vision systems and the write path of the laser in the case of marking machines and the part pick apparatus in the case of pick and place machines. The same sort of problems exist in other automated manufacturing machines in which these sensors are employed.
It would therefore be desirable to have a sensor mounting apparatus which allows a sensor to be pivoted out of the way to allow for removal, replacement and/or maintenance of the underlying tooling and then subsequently pivoted back into position having the sensor in close proximity to the underlying tooling and accurately positioned to prevent the need for recalibration. Additionally, it would be desirable to have a sensor mounting apparatus which positions the sensor in a position other than either directly above the part path or directly to the side of the part path.